Question 1

Which graph best describes how the vapor pressure of a substance varies with temperature according to the Clausius-Clapeyron equation? ln(P) is plotted on the y-axis, and 1/T is plotted on the x-axis. The origin (0, 0) is not necessarily located where the axes cross. 
A) I
B) II
C) III
D) IV

Accepted Answer

According to the Clausius-Clapeyron equation, there is a linear relationship between ln(P) and 1/T. This means that the graph should be a straight line when ln(P) is plotted on the y-axis and 1/T is plotted on the x-axis. The slope of the line is related to the enthalpy of vaporization of the substance. Choice II is the only graph that shows a straight line relationship between ln(P) and 1/T.

Question 2

What is the vapor pressure of an aqueous solution that has a solute mol fraction of  = 0.100? The vapor pressure of water is 25.756 mm Hg at 25°C.
A) 23.2 mm Hg
B) 2.58 mm Hg
C) 25.8 mm Hg
D) 0.900 mm Hg
E) 22.3 mm Hg

Accepted Answer

A

Question 3

Which intermolecular interactions are likely to result in the highest vapor pressure of a substance?
A) dispersion interactions
B) dipole-dipole interactions
C) hydrogen bonds
D) ion-dipole interactions
E) ion-ion interactions

Accepted Answer

Dispersion interactions are the weakest intermolecular forces, but they act on all molecules regardless of polarity or electronegativity. Therefore, substances with only dispersion forces have relatively high vapor pressures because their molecules can easily escape from the liquid phase. Substances with stronger intermolecular forces like dipole-dipole interactions, hydrogen bonds, ion-dipole interactions, and ion-ion interactions have lower vapor pressures because their molecules are more strongly attracted to each other and require more energy to escape from the liquid phase.

Question 4

Which statement about the vapor pressure of a liquid is not correct?
A) The vapor pressure increases with increasing temperature because more molecules have sufficient energy to overcome the attractive forces that hold them in the liquid.
B) The vapor pressure decreases with increasing strength of intermolecular interactions.
C) The pressure at which the rate of molecules evaporating equals the rate of molecules condensing is called the vapor pressure.
D) Adding a nonvolatile solute to a liquid increases the vapor pressure.
E) The enthalpy of vaporization determines how sensitive the vapor pressure of a substance is to a change in temperature.

Accepted Answer

Adding a nonvolatile solute to a liquid decreases the vapor pressure according to Raoult's law. The other statements are correct.

Question 5

Indicate which aqueous solution has the lowest vapor pressure. A) 0.1 M KCl B) 0.1 M Na₂CO₃ C) 0.2 M NaCl D) 0.1 M MgCl₂ E) 0.2 M MgCl₂

Accepted Answer

The vapor pressure of a solution is primarily determined by the concentration of solute particles in the solution because solute particles lower the vapor pressure by inhibiting the escape of solvent molecules into the gas phase. Among the given options, 0.2 M MgCl₂ will dissociate into three ions (1 Mg²⁺ and 2 Cl⁻) per formula unit, resulting in the highest number of particles in solution. Since option E has the highest concentration of a solute that dissociates into multiple particles, it will have the lowest vapor pressure due to the highest decrease in vapor pressure relative to the pure solvent.

Question 6

A solution contains 6.50 mol water, 0.300 mol sucrose, and 0.200 mol glucose. The solutes are nonvolatile. What is the vapor pressure of the solution at 35°C given that the vapor pressure of water is 42.2 torr?
A) 35.0 torr
B) 36.0 torr
C) 37.0 torr
D) 39.2 torr
E) 39.0 torr

Accepted Answer

Since the solutes are nonvolatile, the vapor pressure of the solution is determined solely by the amount of water present. We can use Raoult's Law to calculate the vapor pressure of the solution:

P = X_water * P° water

where P is the vapor pressure of the solution, X_water is the mole fraction of water, and P° water is the vapor pressure of pure water at the same temperature (in this case, 35°C).

First, we need to calculate the mole fraction of water in the solution:

total moles = 6.50 mol + 0.300 mol + 0.200 mol = 7.00 mol
X_water = 6.50 mol / 7.00 mol = 0.929

Next, we can substitute into Raoult's Law:

P = 0.929 * 42.2 torr = 39.2 torr

Therefore, the vapor pressure of the solution at 35°C is 39.2 torr (Choice D).

Question 7

A solution is prepared by adding 1.50 mol glucose, which is not volatile, to 3.50 mol water. What is the vapor pressure of this solution at 25°C given that the vapor pressure of pure water is
23)8 torr?
A) 7.00 torr
B) 16.7 torr
C) 10.2 torr
D) 7.14 torr
E) 34.0 torr

Accepted Answer

The vapor pressure of the solution can be calculated using Raoult's Law: P_solution = X_solvent * P_pure_solvent. The mole fraction of water (solvent) is 3.50 / (1.50 + 3.50) = 0.7. Therefore, P_solution = 0.7 * 23.8 torr = 16.7 torr.

Question 8

Which graph best describes how the vapor pressure of a solution varies according to Raoult's law as a nonvolatile solute is added to a liquid? The vapor pressure of the solution is plotted on the y-axis, and the mole fraction of solute is plotted on the x-axis. The origin (0, 0) is not necessarily located where the axes cross. 
A) I
B) II
C) III
D) IV

Accepted Answer

According to Raoult's law, the vapor pressure of a solution decreases as the mole fraction of solute increases. This relationship is linear, as shown in Graph II. Graphs I, III, and IV do not follow this linear relationship.

Question 9

Indicate which aqueous solution has the slowest evaporation rate. A) 0.1 M KCl B) 0.2 M Na₂CO₃ C) 0.2 M NaCl D) 0.1 M MgCl₂ E) 0.1 M NaBr

Accepted Answer

The compound "Na₂CO₃" is not a valid chemical formula, so it cannot be determined what its properties are. However, assuming it is a typo and meant to be Na2B12O17, this compound has a very low solubility in water, meaning the solution will be less concentrated and evaporate more slowly than the other options.

Question 10

Which intermolecular interactions are likely to result in the lowest vapor pressure of a substance?
A) dispersion interactions
B) dipole-dipole interactions
C) hydrogen bonds
D) ion-dipole interactions
E) ion-ion interactions

Accepted Answer

The answer of Which intermolecular interactions are likely to result...

Question 11

Indicate which aqueous solution has the highest vapor pressure. A) 0.1 M KCl B) 0.2 M Na₂CO₃ C) 0.2 M NaCl D) 0.1 M MgCl₂ E) 0.2 M MgCl₂

Accepted Answer

Vapor pressure of a solution is inversely related to the concentration of solute particles in the solution. 0.1 M KCl has the lowest concentration of solute particles among the options, leading to the highest vapor pressure.

Question 12

Which statement below regarding vapor pressure is not correct?
A) Vapor pressure is an intensive property.
B) The substance with the stronger intermolecular forces has the lower vapor pressure.
C) Vapor pressure increases with increasing temperature.
D) Pure water has a higher vapor pressure at a given temperature than seawater.
E) A nonvolatile solute increases the vapor pressure of the solvent.

Accepted Answer

A nonvolatile solute decreases the vapor pressure of the solvent due to the colligative property effect, which is contrary to what option E suggests.

Question 13

A solution is prepared by adding 0.300 mol glucose, which is not volatile, to 4.50 mol water. What is the vapor pressure of this solution at 25°C given that the vapor pressure of pure water is
23)8 torr?
A) 9.38 torr
B) 22.3 torr
C) 23.4 torr
D) 1.49 torr
E) 22.5 torr

Accepted Answer

The answer of A solution is prepared by adding 0.300...

Question 14

In the diagram below, one beaker contains pure water and the other contains an equal volume of seawater. Seawater has various salts dissolved in it. The beakers are sitting in a totally enclosed chamber, and the outside temperature and pressure are held constant. Identify the statements below about this situation that are not correct.  
I. Water will be transferred from the pure water beaker to the seawater beaker.
II. Water will be transferred from the seawater beaker to the pure water beaker.
III. The vapor pressure of the pure water is higher than the vapor pressure of the seawater.
IV. Pure water evaporates at a faster rate than seawater.
V. Water in the gas phase condenses into both beakers at the same rate.
A) II only
B) II and V
C) II, IV, and V
D) II, III, and IV
E) I, III, and IV

Accepted Answer

I is incorrect because the seawater contains dissolved salts, which will lower its vapor pressure and make it less likely for water to evaporate from it. 
II is correct because water will move from the pure water beaker to the seawater beaker due to osmosis, as the seawater has a higher concentration of solutes. 
III is incorrect because the vapor pressure of seawater is actually lower than the vapor pressure of pure water due to the presence of dissolved salts. 
IV is incorrect for the same reason as I, and in fact, seawater will generally evaporate more slowly than pure water. 
V is incorrect because the vapor in the chamber will tend to condense more in the pure water beaker, again due to the higher vapor pressure of pure water.

Question 15

Which graph best describes how the vapor pressure of a solution varies according to Raoult's law as a nonvolatile solute is added to a liquid? The vapor pressure of the solution is plotted on the y-axis, and the mole fraction of solvent is plotted on the x-axis. The origin (0, 0) is not necessarily located where the axes cross. 
A) I
B) II
C) III
D) IV

Accepted Answer

The answer of Which graph best describes how the vapor...

Question 16

Which statement about how the vapor pressure (P) of a liquid depends on temperature is correct? A) The larger the enthalpy of vaporization, the smaller the change in vapor pressure for a given change in temperature. B) A graph of P versus 1/T is linear with a slope -$\Delta$H_vap/R. C) The smaller the intermolecular interactions, the greater the change in vapor pressure for a given change in temperature. D) A graph of ln(P) versus T is linear with a slope -$\Delta$H_vap/R. E) A graph of ln(P) versus 1/T is linear with a slope -$\Delta$H_vap/R.

Accepted Answer

The Clausius-Clapeyron equation describes the relationship between vapor pressure and temperature, showing that a plot of ln(P) versus 1/T is linear with a slope of -ΔH_vap/R.

Question 17

Which of the solutions shown here will have the lowest vapor pressure? White circles indicate solvent molecules; black circles indicate molecules of a nonvolatile solute.
A) 
B) 
C) 
D)

Accepted Answer

The answer of Which of the solutions shown here will...

Question 18

Which statement about the vapor pressure of a liquid is not correct?
A) The vapor pressure increases with increasing temperature because more molecules have sufficient energy to overcome the attractive forces that hold them in the liquid.
B) The vapor pressure increases with increasing strength of intermolecular interactions because molecules are better able to pull each other into the gas phase.
C) The pressure at which the rate of molecules evaporating equals the rate of molecules condensing is called the vapor pressure.
D) Adding a nonvolatile solute to a liquid decreases the vapor pressure.
E) The enthalpy of vaporization determines how sensitive the vapor pressure of a substance is to a change in temperature.

Accepted Answer

The statement "The vapor pressure increases with increasing strength of intermolecular interactions because molecules are better able to pull each other into the gas phase" is incorrect. Intermolecular interactions, such as hydrogen bonding, dipole-dipole forces, and London dispersion forces, actually make it more difficult for the molecules to overcome the attractive forces and enter the gas phase, resulting in a lower vapor pressure.

Question 19

In the diagram below, one beaker contains pure water and the other contains an equal volume of seawater. Seawater has various salts dissolved in it. The beakers are sitting in a totally enclosed chamber, and the outside temperature and pressure are held constant. Identify the statements below about this situation that are not correct.  I. Water will be transferred from the pure water beaker to the seawater beaker.
II) The vapor pressure of the seawater is higher than the vapor pressure of the pure water.
III) Pure water evaporates at a faster rate than seawater.
IV) Water in the gas phase condenses into the seawater beaker at a faster rate than into the pure water beaker.
A) I, III, and IV
B) II, III, and IV
C) II and III
D) II and IV
E) II only

Accepted Answer

The answer of In the diagram below, one beaker contains...

Question 20

Which of the solutions shown here will have the highest vapor pressure? White circles indicate solvent molecules; black circles indicate molecules of a nonvolatile solute.
A) 
B) 
C) 
D)

Accepted Answer

The solution with only solvent molecules (A) will have the highest vapor pressure because the addition of a nonvolatile solute (represented by the black circles) will lower the vapor pressure of the solution. In solutions B, C, and D, the concentration of the nonvolatile solute increases, leading to a decrease in vapor pressure.

Quiz 11: Solutions: Properties and Behavior

Which graph best describes how the vapor pressure of a substance varies with temperature according to the Clausius-Clapeyron equation? ln(P) is plotted on the y-axis, and 1/T is plotted on the x-axis. The origin (0, 0) is not necessarily located where the axes cross.

Which intermolecular interactions are likely to result in the highest vapor pressure of a substance?

Which statement about the vapor pressure of a liquid is not correct?

Indicate which aqueous solution has the lowest vapor pressure.

A solution contains 6.50 mol water, 0.300 mol sucrose, and 0.200 mol glucose. The solutes are nonvolatile. What is the vapor pressure of the solution at 35°C given that the vapor pressure of water is 42.2 torr?

A solution is prepared by adding 1.50 mol glucose, which is not volatile, to 3.50 mol water. What is the vapor pressure of this solution at 25°C given that the vapor pressure of pure water is 23) 8 torr?

Indicate which aqueous solution has the slowest evaporation rate.

Which intermolecular interactions are likely to result in the lowest vapor pressure of a substance?

Indicate which aqueous solution has the highest vapor pressure.

Which statement below regarding vapor pressure is not correct?

A solution is prepared by adding 0.300 mol glucose, which is not volatile, to 4.50 mol water. What is the vapor pressure of this solution at 25°C given that the vapor pressure of pure water is 23) 8 torr?

Which statement about how the vapor pressure (P) of a liquid depends on temperature is correct?

Which of the solutions shown here will have the lowest vapor pressure? White circles indicate solvent molecules; black circles indicate molecules of a nonvolatile solute.

Which statement about the vapor pressure of a liquid is not correct?

Which of the solutions shown here will have the highest vapor pressure? White circles indicate solvent molecules; black circles indicate molecules of a nonvolatile solute.